Bottom Line:
The fermented M. charantia juice consistently reduced glucose production by 27.2%, 14.5%, 17.1% and 19.2% at 15-minute intervals respectively, when compared against the negative control.This putative anti-diabetic activity can be attributed to the increase in availability and concentration of aglycones as well as other phenolic compounds resulting from degradation of glycosidic momordicoside.Biotransformation of M. charantia fruit juice via lactic acid bacterium fermentation reduced its bitterness, reduced its sugar content, produced aglycones and other metabolites as well as improved its inhibition of α-glucosidase activity compared with the fresh, non-fermented juice.

ABSTRACTLactobacillus plantarum BET003 isolated from Momordica charantia fruit was used to ferment its juice. Momordica charantia fresh juice was able to support good growth of the lactic acid bacterium. High growth rate and cell viability were obtained without further nutrient supplementation. In stirred tank reactor batch fermentation, agitation rate showed significant effect on specific growth rate of the bacterium in the fruit juice. After the fermentation, initially abundant momordicoside 23-O-β-Allopyranosyle-cucurbita-5,24-dien-7α,3β,22(R),23(S)-tetraol-3-O-β-allopyranoside was transformed into its corresponding aglycone in addition to the emergence of new metabolites. The fermented M. charantia juice consistently reduced glucose production by 27.2%, 14.5%, 17.1% and 19.2% at 15-minute intervals respectively, when compared against the negative control. This putative anti-diabetic activity can be attributed to the increase in availability and concentration of aglycones as well as other phenolic compounds resulting from degradation of glycosidic momordicoside. Biotransformation of M. charantia fruit juice via lactic acid bacterium fermentation reduced its bitterness, reduced its sugar content, produced aglycones and other metabolites as well as improved its inhibition of α-glucosidase activity compared with the fresh, non-fermented juice.

Mentions:
Hydrolysis of momordicoside during fermentation of L. plantarum BET003 culture in M. charantia fresh juice was investigated. After 24 hr fermentation under optimum condition, initially abundant momordicoside identified as 23-O-β-Allopyranosyle-cucurbita-5,24-dien-7α,3β,22(R),23(S)-tetraol-3-O-β-allopyranoside (compound A, 2.1 ± 0.2 mg/mL) was totally absent (Fig. 6A). The concentration of its corresponding aglycones was increased and there were other new metabolites produced via biotransformation during the fermentation process. In this study, a metabolite known as methyl 2-[cyclohex-2-en-1-yl(hydroxy)methyl]-3-hydroxy-4-(2-hydroxyethyl)-3-methyl-5-oxoprolinate (compound B) was significantly produced at the end of fermentation ∼2.5 ± 0.2 mg/mL (Figs. 6B–6D). The results suggested that stoichiometric conversion of compound A to compound B and other phenolic compounds over the course of the whole fermentation period may have occurred. Compound A was hypothesized to be converted to compound B via enzyme hydrolysis from L. plantarum BET003 which involves a two-step process. The first step was attributed to glucosidase-like enzymatic hydrolysis of the glycosidic linkage to release the aglycone. After the glycosidic linkage was completely hydrolyzed, compound B and other phenolic compounds materialized. The second step could have involved esterase activities that hydrolyzes the ester to acid and alcohol (Marsilio, Lanza & Pozzi, 1996). While the two-step enzymatic hydrolysis hypothesis is plausible, further studies need to be carried out in order to confirm the conversion route. Fermentation of M. charantia juice also produced other phenolic compounds such as ellagic acid as other major products. Ellagic acid was observed at 12 and 24 hr fermentation time. Jasmonic acid was detected after 6 hr but disappeared at 12 hr fermentation time until the end. Biotransformation of other saponin-containing plant such as ginseng and soya bean with lactic acid bacteria that modified their phytochemical profiles resulting in improved bioactive properties have been reported (Bae et al., 2004; Gurfinkel & Rao, 2003). Rg3, a percusor of Rh2 ginsenoside, showed a potent antitumor properties but due to its extremely low concentration in normal ginseng, Rg3 was produced via biotransformation by lactic acid fermentation (Cheng et al., 2008). The aglycone of soyasaponin called soyasapogenol, was more cytotoxic toward cancer cells compared with its glycosides form (Gurfinkel & Rao, 2003). Biotransformation of soyasaponin by Lactobacillus rhamnosus has been reported to occur at specific time points and resulted in different phytochemical profiles (Zhang et al., 2012). Thus, by controlling the fermentation time, specific phytochemical profile may be obtained and desirable products could be enhanced through optimization.

Mentions:
Hydrolysis of momordicoside during fermentation of L. plantarum BET003 culture in M. charantia fresh juice was investigated. After 24 hr fermentation under optimum condition, initially abundant momordicoside identified as 23-O-β-Allopyranosyle-cucurbita-5,24-dien-7α,3β,22(R),23(S)-tetraol-3-O-β-allopyranoside (compound A, 2.1 ± 0.2 mg/mL) was totally absent (Fig. 6A). The concentration of its corresponding aglycones was increased and there were other new metabolites produced via biotransformation during the fermentation process. In this study, a metabolite known as methyl 2-[cyclohex-2-en-1-yl(hydroxy)methyl]-3-hydroxy-4-(2-hydroxyethyl)-3-methyl-5-oxoprolinate (compound B) was significantly produced at the end of fermentation ∼2.5 ± 0.2 mg/mL (Figs. 6B–6D). The results suggested that stoichiometric conversion of compound A to compound B and other phenolic compounds over the course of the whole fermentation period may have occurred. Compound A was hypothesized to be converted to compound B via enzyme hydrolysis from L. plantarum BET003 which involves a two-step process. The first step was attributed to glucosidase-like enzymatic hydrolysis of the glycosidic linkage to release the aglycone. After the glycosidic linkage was completely hydrolyzed, compound B and other phenolic compounds materialized. The second step could have involved esterase activities that hydrolyzes the ester to acid and alcohol (Marsilio, Lanza & Pozzi, 1996). While the two-step enzymatic hydrolysis hypothesis is plausible, further studies need to be carried out in order to confirm the conversion route. Fermentation of M. charantia juice also produced other phenolic compounds such as ellagic acid as other major products. Ellagic acid was observed at 12 and 24 hr fermentation time. Jasmonic acid was detected after 6 hr but disappeared at 12 hr fermentation time until the end. Biotransformation of other saponin-containing plant such as ginseng and soya bean with lactic acid bacteria that modified their phytochemical profiles resulting in improved bioactive properties have been reported (Bae et al., 2004; Gurfinkel & Rao, 2003). Rg3, a percusor of Rh2 ginsenoside, showed a potent antitumor properties but due to its extremely low concentration in normal ginseng, Rg3 was produced via biotransformation by lactic acid fermentation (Cheng et al., 2008). The aglycone of soyasaponin called soyasapogenol, was more cytotoxic toward cancer cells compared with its glycosides form (Gurfinkel & Rao, 2003). Biotransformation of soyasaponin by Lactobacillus rhamnosus has been reported to occur at specific time points and resulted in different phytochemical profiles (Zhang et al., 2012). Thus, by controlling the fermentation time, specific phytochemical profile may be obtained and desirable products could be enhanced through optimization.

Bottom Line:
The fermented M. charantia juice consistently reduced glucose production by 27.2%, 14.5%, 17.1% and 19.2% at 15-minute intervals respectively, when compared against the negative control.This putative anti-diabetic activity can be attributed to the increase in availability and concentration of aglycones as well as other phenolic compounds resulting from degradation of glycosidic momordicoside.Biotransformation of M. charantia fruit juice via lactic acid bacterium fermentation reduced its bitterness, reduced its sugar content, produced aglycones and other metabolites as well as improved its inhibition of α-glucosidase activity compared with the fresh, non-fermented juice.

ABSTRACTLactobacillus plantarum BET003 isolated from Momordica charantia fruit was used to ferment its juice. Momordica charantia fresh juice was able to support good growth of the lactic acid bacterium. High growth rate and cell viability were obtained without further nutrient supplementation. In stirred tank reactor batch fermentation, agitation rate showed significant effect on specific growth rate of the bacterium in the fruit juice. After the fermentation, initially abundant momordicoside 23-O-β-Allopyranosyle-cucurbita-5,24-dien-7α,3β,22(R),23(S)-tetraol-3-O-β-allopyranoside was transformed into its corresponding aglycone in addition to the emergence of new metabolites. The fermented M. charantia juice consistently reduced glucose production by 27.2%, 14.5%, 17.1% and 19.2% at 15-minute intervals respectively, when compared against the negative control. This putative anti-diabetic activity can be attributed to the increase in availability and concentration of aglycones as well as other phenolic compounds resulting from degradation of glycosidic momordicoside. Biotransformation of M. charantia fruit juice via lactic acid bacterium fermentation reduced its bitterness, reduced its sugar content, produced aglycones and other metabolites as well as improved its inhibition of α-glucosidase activity compared with the fresh, non-fermented juice.